Electromagnetic radiation is radiant energy released by certain electromagnetic processes, including radio waves, microwaves, infrared (IR) light, visible light, ultraviolet (UV) light, X-rays, and gamma rays. In classical physics, electromagnetic radiation consists of waves, which are oscillations of electric and magnetic fields. Such electromagnetic waves are characterized by wavelength or frequency, which determines position on the electromagnetic spectrum. The electromagnetic spectrum runs from long large wavelength, low energy radio waves, to short wavelength, high-energy gamma rays. In quantum physics, electromagnetic radiation is described in terms of elementary particles, called photons, instead of waves.
Electromagnetic radiation forms the backbone of many modern technologies, including but not limited to, radio transmitters, microwave transmitters, X-ray equipment, and high power lasers. A key challenge in using these technologies is accurately measuring or monitoring power output. In many cases, features such as high energy levels can make it particularly difficult to accurately measure electromagnetic radiation. This difficulty in making accurate measurements has implications in many areas, such as industries where high power lasers are used in industrial processes, and in scientific research and medicine where research and treatments rely on accurate measurement of the X-ray flux.
A key challenge in the use of high-power lasers is accurately measuring and monitoring power. Current techniques used for measuring and calibrating high-power lasers involve calorimetric approaches, where incident optical energy is absorbed by a known quantity of material, and power is calculated based on the rise in temperature over time. This approach relies on a temperature response that is linear relative to the incident power absorbed. However, a key limitation is the slow response time of such methods. Another approach to determining optical power involves a flowing water method, where water is heated by the incident optical power. This method provides a more rapid response, but the size of the monitoring system must scale linearly with the power being measured. Both the calorimetric and flowing water methods require that the majority of optical power be absorbed in order to provide an accurate power reading. Another drawback of such systems is that they are not portable.
Recently, U.S. Patent Application Publication No. 2014/0307253 to Williams, et al., “Use of Radiation Pressure For Measurement of High-Power Laser Emission,” Optics Letters, 38(20):4248-51 (2013), described an approach to measuring laser power via radiation pressure or force. That approach involves directing a laser beam at a direct-loading force-restoration balance having a resolution of 100 nN. The laser beam is directed incident to a mirror that is attached to the shaft of the balance, and the force of the laser beam is measured by deflection of the shaft. While such a system represents an improvement versus calorimetric approaches to measuring laser power, it suffers from drawbacks including inherent noise due to temperature drifts and ambient air movements. These drawbacks overly complicate the direct-loading force-restoration balance approach to measuring laser power.
Another area where there are challenges, similar to those encountered in measuring power from high power lasers, is in measuring X-ray flux. For example, at synchrotrons and free-electron laser facilities, the measurement of X-ray flux is necessary to align and troubleshoot optical elements. However, measuring the X-ray flux is a complicated endeavor, requiring significant time and resources that impacts research.
Likewise the accurate measurement of photon flux from an X-ray source is important for radiation therapy centers, where such measurement is key to calculating absorbed dose at a target tissue. Technologies used to measure X-ray at synchrotrons, free-electron laser facilities, and radiation therapy centers include ion chambers and diode arrays. However, these techniques have inherent limitations.
For radiation therapy, these techniques are based on dosage measurement at a specific point, which may or may not correlate with tumor volume. Such techniques have serious limitations with regard to Intensity Modulate Radiation Therapy where treatment requires dosage modulation as described in Schreiner, L. J., “On The Quality Assurance and Verification of Modern Radiation Therapy Treatment,” J. Med. Phys. 36(4):189-91 (2011).
Thus, there is a need for new methods and devices for measuring and monitoring photonic pressure that can be used wherein the photonic pressure is created from electromagnetic sources, including but not limited to X-Rays, UV light, visible light, and infrared light.
The present technology is directed to overcoming these and other deficiencies in the art.